Study On The Tradeoff Between The Benefits Of Ecological Flow And Optimal Trans-Basin Water Resources Management

The optimal reservoir operation in the Trans-basin water diversion project can realize the reasonable allocation of interregional water resources.However,it is urgent to solve the problem of how to balance the ecological flow and the demand of water resources for the economic development.Therefore,this paper take the Hanjiang-Weihe River Water Transfer Project using for example.It is of great theoretical and practical value to study the optimal ecological reservoir operation based on the benefit equilibrium analysis.At first,this paper studies the operation rules of the Hanjiang-Weihe River Water Transfer Project,which provides the foundation for establishing the optimal reservoir operation model of the Hanjiang-Weihe River Water Transfer Project including the new water source of the Jialing-Hanjiang River Water Transfer Project.Secondly,through the collection of the long series of runoff data,using the SPI method and the stochastic flow duration curves to calculate the long series of ecological flow of the Lveyang water intake of Jialing river.Thirdly,the optimal reservoir operation model of the Hanjiang-Weihe River Water Transfer Project including the new water source was established by considering the constraint of ecological flow,and the model was solved by using the ICS algorithm.Finally,the analysis of the ecological benefits of the Jialing River to recommend the water transfer quantity of Lveyang.The research results of this paper mainly include the following aspects:(1)Through the study of the ecological flow,a method to calculate the ecological flow is proposed,which considers the distribution of the interannual runoff.This method uses SPI index and stochastic flow duration curve to obtain the typical year series of ecological flow.The typical year series of ecological flow relative to the planning design value,its adaptability have been significantly improved.(2)The optimal reservoir operation model of the Hanjiang-Weihe River Water Transfer Project including the new water source was established,and it was solved by using ICS algorithm.The project could be used to supplement the available water quantity of the Hanjiang-Weihe River Water Transfer Project and improve the probability of water supply.The water diversion flow of Jialing-Hanjiang River Water Transfer Project is 40m3/s to 50 m3/s could meet the requirements of 95%water supply probability,it's multi-year average water supply is 540 million m3 to 6.1 billion m3.(3)This paper using nonparametric Mann-kendall method to test the runoff variation in the downstream of the Lveyang of Jialing River.The runoff of Lveyang was changed obviously in the late the 1990s,and the variational year was 1994.By analyzing the runoff characteristics before and after the variation,the runoff process of the Lveyang is not only a trend of decreasing annual runoff,but also a great change in distribution in the annual year.The magnitude and duration of the extreme flow are extremely changed,and the distribution of runoff is more homogeneous in the annual year.(4)According to the variation of before and after,the impact of water transfer project on the Jialing River runoff is divided into two stages.When the amount of water diversion flow is increased by 30m3/s to 40m3/s,most of the indexes show obvious abrupt changes from moderate to high,and their influence on the minimum characteristic flow is greater than that of the maximal characteristic flow.Through the analysis of the mutual influence between the ecological benefit and the water transfer in the Lveyang of Jialing River,the paper concludes that the water diversion flow of the Jialing-Hanjiang River Water Transfer Project is 40m3/s and could meet the requirements of ecological flow and water division flow,and the tradeoff solution between the ecological benefits and the water transfer benefits is obtained.